Elongation Definition - Demtech Pro-Tester T-0100 Operator's Manual

Rev B: December 2006
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4. Elongation Definition
If you intend to use the strain (elongation) feature of the Pro-Tester™ tensiometer it is important
to understand both the definition of this feature/function and how it is intended to be used.
Proper understanding requires the definition of some basic terms. These terms are defined
below.
Grip Separation (GS): The distance between the grip point on each of the left and right
sample grip assemblies (refer to Figure 4). There are two user settable distances, A or B,
which have been factory set for 1.7 and 3.5 inches respectively. The operator must be aware
of these values and change the settings if necessary (refer to Section 3.4) to accommodate the
particular sample to be tested.
Weld Extrusion (Squeeze-out):
The area of a weld whereupon becoming molten the parent
material extrudes (is squeezed) out from between the pressure zone of the welding tool and
then cools. This extruded material does not usually provide an acceptable bond of the parent
material and should not be considered part of the weld (refer to Figure 5C).
Weld Width (WW): The center-to-center distance between the two welds of a dual-track
weld (refer to Figure SA) or the edge-to-edge distance on a solid weld (refer to Figure 5B). It
is important when measuring/calculating these distances that the operator only include the
actual width of the weld. The width of the weld is defined as only that area where the two
sheets of parent material have been appropriately bonded by both heat and pressure. During
this process some parent material may extrude beyond the pressure zone of the welding tool
(refer to Weld Extrusion definition). This extruded material does not usually provide an
acceptable bond of the parent material and should therefore be excluded from any
measurements made for this test.
Gauge Length (GL):
This is the base value used by the Pro-Tester™ for determining
elongation percentage. It is the Grip Separation once the initial tension value has been
reached minus the Weld Width (GS- WW = GL). For example if your Grip Separation was
4 inches and your Weld Width was 1 1/2 inches then your Gauge Length would be 2 1/2
inches (4 - 1.5 = 2.5). It is this value that is used to determine elongation. Elongation is
calculated as the percentage of change (increase) of the Grip Separation related to Gauge
Length. For example ifyour Gauge Length is 2 1/2 inches and the grips had separated 1 1/4
inches at the completion of your test then the elongation would be 50% (1.25
I
2.5 =.50). If
Page 9 Pro-Tester™ Operator' s Manual T-Manual
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